Drilling and belling apparatus

ABSTRACT

Apparatus for drilling a hole, and for belling out the lower end of the hole into a conical enlargement, in a single pass of the apparatus down the drill hole, which apparatus includes a combined drilling and belling tool. Both the extension and the retraction of the belling blades are positively driven. The combined drilling and belling tool is characterized by the fact that the drilling blades are adapted to cut in one direction of rotation, while the belling blades are adapted to cut in the opposite direction of rotation.

[ Sept. 11, 1973 .1; fill 175/267-269, 263, 272, 273, 284, 285

Robert L. Pereau, Irvine, Calif.

Assignee: Smith International, Inc., Newport Beach, Calif.

Sept. 1, 1971 Appl. No.: 177,037

References Cited UNITED STATES PATENTS United States Patent [191 Pereau DRILLING AND BELLING APPARATUS I [75] Inventor:

Filed:

U.S. Cl.............

Int.

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saw 13 or 15 DRILLING AND BELLING APPARATUS BACKGROUND OF THE INVENTION In construction work it is often the practice to construct a footing or foundation member whose lower end portion is enlarged. Such footings are commonly constructed of reinforced concrete in which the steel reinforcing material provides the tensile strength which would otherwise be lacking. Enlargement of the lower end of the footing not only adds to the weight and hence the stability of the footing, but also provides a positive restraint against any upward pull on the footing. I

One particular application of the present invention is in construction of ocean platforms to be used for oil prospecting or drilling operations. The ocean platform may be subjected to very strong ocean waves which place severe stresses on the platform'legs in both horizontal and vertically upward directions. Furthermore, the work of constructing such a platform must be performed under conditions which are rather adverse, hence there is a high premium on efi'iciency in the initial performance of the construction work.

The art of drilling holes for reinforced footings, whether on land or under the ocean floor, has hitherto been well known. It has also been well known, after the initial hole has been drilled, to bell out or enlarge the lower end of the hole. However, the belling out of the down the hole.

A more specific object of the invention is to provide such an apparatus which is suitable for use in constructing an ocean platform.

DRAWING SUMMARY FIG. 1 is an elevational view ofjfootings supporting a temporary ocean platform, in a typical ocean platform construction job where the apparatus of the present invention may be used;

FIGS. 2a, 2b and 20 together are an elevation view of the apparatus of the present invention, shown in use in the center of FIG. 1 for constructing a footing;

FIGS. 3a and 3b together show an elevational crosssectional view of the swivel assembly and kelly bar assembly, taken on the line 3-3 of FIG. 2;

FIG. 4 is an elevational view'of the kelly bar assembly taken on the line4-4 of FIG. 3;

FIG. 5 is a transverse cross-sectional view taken on the line 5-5 of FIG. 3a;

FIG. 6 isa transverse cross-sectional view taken on the line 6-6 of FIG. 3b; I I

FIG. 7 is a transverse cross-sectional view taken on the line 7-7 of FIG. 3b;

FIGS. 8a, 8b, 8c and 8d together are an elevational view, partially in cross-section, of the drill stem assembly and combination drilling and belling tool;

FIGS. 9a, 9b, 9c and 9d together are a vertical crosssectional view of the drill stem assemblyand combina: tion drilling and belling tool taken on the lines 9-9 of FIG. 8;

FIG. l0.is a transverse cross-sectional view taken on the line 10-10 of FIG. 9a;

FIG. 15 is a transverse cross-sectional view taken on the line 15-15 of FIG. 9b;

FIG. 16 is a transverse cross-sectional view taken on the line 16-16 of FIG.

FIG. 17 is atransverse cross-sectional view taken on the line 17-17 of FIG. 90;

FIG. 18 is a transverse cross-sectional view taken on the line 18-18 of FIG. 9d;

FIG. 19 is a transverse cross-sectional view taken on the line 19-19 of FIG. 9d;

FIG. 20 is an exploded perspective view of the tubular casing of FIG. 8a showing above the casing a section of drill stern which is adapted for reverse circulation with air lift;

FIG. 21 is a perspective view, partially in crosssection, of the kelly bar assembly of FIGS. 24, 3b and FIG. 22 is an elevational cross-sectional view of the drilling and belling tool taken on the linen-22 of FIG. 17; v FIG. 23 is an enlarged fragmentary cross-sectional view of one of the belling blades taken on the line 23-23 of FIG. 22;

FIG. 24 isan enlarged fragmentary cross-sectiona view taken on the line 24-24 of FIG. 23

FIG. 25 is an elevational cross-sectional view taken on the line 25-25 of FIG. 18;

FIG. 26 is an enlarged fragmentary cross-sectional view taken on the line 26-26 of FIG. 25;

FIG. 27 is an exploded perspective view of the belling blade and carriage portions of the combined drilling and belling tool;

FIG. 28 is an elevational view of the combined drilling and belling tool showing the belling blades in their extended position;

FIG. 29 is an enlarged detail view showing the tooth locations for thebelling blades;

FIG. 30 is an elevational view of the enlarged lower end of a completed footing; and

FIG. 3.1 is a chart showing the estimated savings achieved by use-of the present invention.

PREFERRED EMBODIMENT General Description The combination drilling and belling tool assembly, FIGS. 20, 2b, and 20, consists of a combination drilling and belling bucket 500, the necessary sections of reverse circulation drill stem withairlift 300, a section of reverse circulation drill stem with air injection 400, the necessary number of stabilizers 375, a kelly bar assembly 200, and a swivel I00.

Referring to FIG. I, in order to make the tool operational it is also necessary to have compressed .air and hydraulic fluid supplies (not shown), a settling tank 14 intowhich the drilling fluid 22 and drilling chips'may be discharged, a return hose 16 for returning the drilling fluid to the drill hole, a tower l8 and block and tackle 24 to support the drill string during the drilling operation, a winch 26 to control the block and tackle,

and a ring gear drive or rotary table which engages the kelly bar 200, and provides the rotary driving force to the drill stem assembly.

Referring to FIGS. 2a, 2b, 2c, and 3a, attached to the top of the kelly bar and drill stem assembly is a reverse circulation swivel 100 consisting of a bail 102, a swivel body 104, an elbow 106 attached to the top of the swivel body, a spindle 108, and a hydraulic swivel housing 110. The bail is provided with a means for pivotally attaching a block and tackle hook 28 at its top and is further provided with a means for the pivotal attachment of the swivel body 104 to its lower end. The spindle is centrally disposed within the swivel body and has a spindle center pipe 1 12 with a swivel flange plate 1 14 attached to its lower end. The swivel body is provided with a sealed cavity 118 surrounding the center pipe of the spindle and connected in a continuous manner to an auxiliary conduit 158 in the spindle. In addition, the purpose of the swivel is to provide the vertical support necessary to support the drilling tool while still allowing the spindle to freely rotate within the swivel body. The elbow 106 attached to the top of the swivel body has an elbow-shaped pipe 120 which acts as a discharge nozzle for the drilling fluid and drilling chips. It should be noted that the vertical displacement of the entire drill string is controlled by the vertical displacement of the swivel. The vertical displacement of the swivel is generally controlled by the attachment of a block and tackle 24 between the top of the drilling tower 18 and the top of the swivel bail 102.

Attached between the top of the drill stem assembly and the swivel is a kelly bar assembly 200. The kelly bar assembly has an elongated tubular frame 202, a center pipe section 204 and an air auxiliary pipe section 206 (FIG. 3b), disposed within the tubular frame, two elongated ribs 208 attached to the outer circumference of the tubular frame, two hydraulic cylinders 210 disposed within the frame, a bracket 212 for coupling the action of the two hydraulic cylinders together, a sucker rod swivel 214 for attachment of the drill stem sucker rod 209 to the hydraulic cylinder bracket 212, and top and bottom adapters 216 and 218 at the top and bottom ends of the kelly bar for attaching the kelly bar assembly 200 between the top of the drill stem assembly and the swivel 100.

The function of the kelly bar assembly 200 is to provide a means for coupling the drill stem assembly to the rotary table 20. This coupling is provided by the elongated ribs 208 on the outside of the kelly bar frame. The kelly bar is free to slide up and down through the rotary table while recesses within the rotary table ring gear engage with the ribs on the outside surface of the kelly bar assembly. Hence, the power drive provided by the rotary table is transmitted to the kelly bar which in turn transmits the rotary action to the drill stem assembly. The two hydraulic cylinders 210 disposed within the kelly bar frame are coupled at their upper or cylinder ends to the frame structure while the lower or piston ends of the cylinders are coupled to the bracket 212, which in turn is coupled to the sucker rod swivel 214. This sucker rod swivel provides connection to the previously mentioned sucker rod 209 which extends up through the drill stem. Hence, by activating the hydraulic cylinders the sucker rod is displaced in a vertical direction relative to the kelly bar and drill stem assemblies.

Attached to the bottom end of the kelly bar assembly is a section of reverse circulation drill stem with airlift 300. It is seen that this section of drill stem consists of a center pipe section 302, two auxiliary pipe sections 304 (FIG. 9a), a tubular casing 306, four transverse openings 308 through the casing, and attachment or drill stern flange plates 310 and 312 at the upper and lower ends of the drill stem section. The center pipe section and auxiliary pipe sections are so oriented that they align with the center pipe section, the auxiliary air pipe section and the sucker rod swivel of the kelly bar assembly.

At least one section of reverse circulation drill stem with air injection 400 is used in the drill string. This section of drill stem is nearly identical to the previously described section of reverse circulation drill stem with airlift 300. Its main components are a center pipe section 402, two auixiliary pipes 404 and 406 (FIGS. 9a and (b), a tubular casing 410, attachment or drill stem flange plates 412 and 4141 at its upper and lower ends, and four transverse openings 416 through the casing. As with the previously described section of drill stern, one of the auxiliary pipes 406 shown in FIG. 9b may be used to house a section of sucker rod 209. This auxiliary pipe is identified as the sucker rod auxiliary pipe. The essential difference between this section of drill stem and the previously described section of drill stem is revealed by examining the function of the other auxiliary pipe 404. At the lower end of the drill stem section is seen a series of drilled holes 418 interconnecting the auxiliary pipe 404 and the center pipe 402 of the drill stem. Hence, as air pressure is applied to this auxiliary pipe it will necessarily flow through these holes into the center pipe. This is known in the art as an air injection process.

Attached at regular intervals along the drill string are stabilizers 375. The stabilizer is a commercially available item and basically consists of a spindle 377 and an outer housing or body assembly 379. The body assembly may be provided with a series of elongated roller bearings such that the body assembly is freely rotatable relative to the spindle. The outside diameter of the body assembly is made to match the diameter of the drill casing 50 and the inside diameter of the spindle is made to be firmly attached to the drill 'stem. Hence, when the stabilizer is firmly attached to the drill stem it acts to center the drill stem within the drill casing. The provision of the elongated roller bearings acting between the spindle and the stabilizer housing allows the drill stem to freely turn within the stabilizer housing while the stabilizer housing is riding against the drill casing.

The attached sections of drill stem assembly. Attached to the bottom of the drill stem assembly is the combination drilling and belling bucket 500. The combination drilling and belling bucket 500 consists of an elongated generally cylindrical bucket frame 502, two belling blades 508 and 509 (FIG. 28), two actuating arms 510 and 511, a carriage assembly 512, and an elongated member 514 attached to the carriage assembly. The bucket frame is seen to consist of an outer shell assembly 504 which is provided with recesses, i.e., rectangular cutouts 522 and 523, for receiving the belling blades. At the bottom of the outer shell assembly is attached a drilling bucket bottom 546. This bucket bottom is a standard drilling bucket bottom and is provided with drilling blades for cutting and removing the soil from within the drill casing 50 as the bucket is rotated in a clockwise direction. The bucket frame outer shell assembly is provided with means for pivotally attaching the belling blades. These pivotal attachments are so oriented that the blades are positioned within the recesses provided in the outer shell of the frame. The

remaining portion of the frame structure is provided by the drill stem assembly 506 which is centrally disposed within the outer shell assembly and is rigidly attached to its upper end. This drill stem assembly has a center pipe 552 which extends to the bottom of the bucket. Disposed between the bucket frame and the center pipe is the carriage assembly 512. The carriage assembly may be vertically displaced relative to the bucket frame. Extending between the carriage frame and each belling blade are two actuating arms 510, 511. One end of each of the actuating arms is pivotally attached to the lower end of the carriage frame. The other end of each of the actuating arms is pivotally attached to its respective belling bucket blade 508 or 509 near the blade longitudinal midpoint. As previously noted, the belling blade'is pivotally attached at its upper end to the bucket frame and is so oriented that the lower end of the belling blade is free to swing into and out of the recess provided in the outer shell of the bucket frame. Attached to the upper end of the carriage assembly is an elongated member 514. This elongated member passes through the bucket drill stem assembly 506 and terminates at the upper end of the bucket drill stem.

From the foregoing description it will be apparent that the operation of the belling blades is controlled by the selective raising and lowering of the carriage assembly. Referring to FIG. 28, the selective raising and lowering of the carriage assembly 512 is accomplished by selectively raising and lowering the elongated member 514. As the carriage assembly is raised, the ends of the actuating arms 510 attached to the carriage assembly are also raised. Because the actuating arm is a rigid member, the structure attached to its other end, that is, the belling blades 508 and 509, must act to accommodate the upward movement of the actuating arm. The only way in which the blade can do this is by rotating about the pivotal attachment at its upper end. Hence, as the carriage assembly is raised the belling blade lower end is moved through an arcuate path away from the bucket frame. As the carriage assembly is lowered the blades are retracted into the recesses within the bucket frame.

In operation, the primary advantage of this tool is that with a single pass a'drill hole of the desired diameter may be drilled to any desired depth and then without removing the tool a conical cavity may be cut at the lower end of the drill hole. Briefly the procedure for doing this is to drill down the desired depth by concurrcntly rotating and lowering the drill stem. It is neces-. sary to add sections of the reverse circulation drill stem with airlil't300 as the drill string lowered, and at selected intervals to also add the stabilizers 375. During the drillingprocess, drilling chip removal is accomplished by the reverse circulation process. In this process pressurized air is connected to the swivel 100. Referring to FIGS. 3b, 9a, and 9b, this air pressure is supplied through the swivel to kelly bar air auxiliary pipe section 206 and hence to one of the drill stem auxiliary pipes 304. Upon reaching .the reverse circulation drill stem with air injection 400, the air is then injected into the center pipe of the drill stem, through the series of drilled holes 418. The air then bubbles up through the center pipes 402 and 302 of the drill stem and kclly bar center pipe 204 into the swivel 100, FIG. 3, and through the elbow discharge nozzle 120 to the settling tank 14, FIG. 1. This air flow creates lift in the center pipe which in turn lifts the drilling fluid from the bottom of the drilling bucket 500 and carries with it the drilling chips as they are cut from the bottom of the drill hole. In this manner, the drilling fluid is carried up through the center pipes of the drill stem and kelly bar to the swivel center pipe and through the discharge nozzle to the settling tank. Drilling fluid is then returned to the drill hole after the drilling chips have settled out. In this manner a reverse circulation is set up whereby the fluid flows down the outside of the drill stem assembly to the bottom of the drill hole and then returns through the center of the drill stem assembly to the settling tank carrying with it the drilling chips.

Once the desired depth of the drill hole is reached, the lowering of the drill string is stopped and the rotation is reversed to the counterclockwise direction. The hydraulic cylinders 210 in the kelly bar assembly 200 are then actuated to pull the sucker rod 209 in a vertical direction. Since the sucker rod 209 is attached to the elongated member 514 of the combination drilling and belling bucket 500, which in turn is attached to the carriage assembly 512, the vertical displacement of the hydraulic cylinders 210 causes the vertical displacement of the carriage assembly 512 relative to the bucket frame 502. As has been previously described, this action causes the belling blades 508 and 509 to extend and, since the rotation of the bucket 500 is continued, the belling blades cut a conical cavity at the botinjectionprocedure is continued, thereby effecting the drilling chip removal in the manner just described. Once the blades have been fully extended, the direction of the hydraulic cylinder travel is reversed causing the sucker rod 209 to reverse the direction of travel of the carriage assembly 512, thereby causing a reversal in the direction of the blade movement. This is continued until the blades are fully returned into the recesses in,

the bucket frame 502.. At this point the drill hole is completed, and the entire drill stem assembly and bucket are removed from the drill hole.

SWIVEL ASSEMBLY Now, the drill string components will be considered in more detail. Attached to the top of and supporting the drill stem and kelly bar assemblies is a reverse circulation swivel 100, FIG. 3a. This swivel has a'bail 102 to which is pivotally attached a swivel body 104. This pivotal attachment is accomplished by pinning two attachment ears 122, which extend from the swivel body, into the clevises 124 provided on the lower ends of the swivel bail. These attachment ears extend from the swivel body lower housing 126. This swivel body lower housing has a center opening 128 and a concentric counter bore 130 in its top surface which extends through a substantial portion of a swivel body lower housing thickness. Disposed within this counter bore is a tapered roller bearing 132. The inside diameter of the tapered roller bearing is approximately the same as the diameter of the center opening in the swivel body lower housing. Disposed within the lower housing and tapered roller bearing is a spindle 108. This spindle has a center pipe 1 12 to which is attached a cylindrical collar 134. This collar has a reduced diameter 136 on its lower portion which matches the inside diameter of the tapered roller bearing. The upper portion of the collar forms a shoulder 138 which seats on the upper surface of the tapered roller bearing. Thus, the spindle 108 is supported in its vertical direction by the seating contact provided between the collar shoulder and the tapered bearing but is still allowed to freely rotate because of the free rotation of the tapered bearing.

Attached to the top of the lower housing is a swivel body upper housing 140. This upper housing has a central opening 142 concentric with the center opening 128 in the lower housing 126. Concentric with this center opening, the upper housing is provided with a counter bore 144 which receives a roller bearing 146. As seen, the center pipe of the spindle extends up into the upper housing and is provided with a reduced diameter 148, which matches the inside diameter of the roller bearing 146 and thereby forms a shoulder 150 against which the roller bearing is seated. In addition, the upper housing is provided with an air chamber 152. This air chamber extends circumferentially around the center opening 142 provided in the upper housing and is in continuous contact with the spindle collar 134. The air chamber is sealed by providing air tight seals 154 and 151 which act between the spindle collar and the upper housing and the spindle center pipe and the upper housing. Air is admitted to this air chamber through an air inlet port 156 which is connected to an air compressor.

The air outlet is provided by a bored hole 158 extending through the spindle collar from its top to its bottom surface. This bored hole extending through the spindle collar is in turn aligned with and concentric to a bored hole 159 in a hydraulic coupling collar 160. The hydraulic coupling collar is a cylindrical collar whose inside diameter matches the outside diameter of the center pipe 112 of the swivel spindle 108. The hydraulic coupling collar is attached to the center pipe and is adjacent to the lower surface of the spindle collar 134. As noted, this hydraulic coupling collar has a bored hole 159 extending through its thickness and aligned with and concentric to the bored hole 158 in the spindle collar 134. Thus, a continuous exhaust port is provided which communicates the air chamber 152 with the bottom of the hydraulic coupling collar.

Attached to the bottom surface of the swivel body lower housing 126, is a hydraulic housing 110. This hydraulic housing has a central opening 162 whose diameter matches the outside diameter of the hydraulic coupling collar 160. Two circumferential grooves 164 are provided at different elevations on the inside surface of the center opening of the hydraulic housing. These circumferential grooves are coupled to hydraulic lines 166 through drilled and tapped holes 168 which extend through the wall of the hydraulic housing and intersect the circumferential grooves. In addition, a seal groove 170 is cut on each side of the previously described circumferential grooves 164., 145, thus forming recesses which receive seals 172 which extend around the outside surface of the hydraulic coupling collar 160 thereby providing a fluid tight seal on each side of the circumferential grooves 164 and 145. Oppositely disposed from the bored hole 159 in the hydraulic coupling collar are two drilled holes 174 and 147. As seen, the drilled hole 174 on the left hand side extends to a depth matching that of the top circumferential groove 164 containing hydraulic fluid. The coupling between this drilled hole and the circumferential groove is achieved by a second drilled hole 173 which is at right angles to the first drilled hole 174 and extends through the wall of the hydraulic collar and intersects the circumferential groove 164 containing the hydraulic fluid. The drilled hole 147 on the right extends to an elevation matching that of the first or lower circumferential groove containing hydraulic fluid. This drilled hole is coupled to the circumferential groove by a second drilled hole 141 extending through the wall of the hydraulic coupling collar and intersecting the circumferential groove 145 containing the hydraulic fluid, but not intersecting the drilled hole coupling the top circumferential groove. In this manner, two entirely independent hydraulic fluid circuits are maintained and coupling from the external hydraulic power supply to the rotating member is achieved.

The center pipe 112 of the spindle extends beyond the bottom of the hydraulic coupling collar to a swivel flange plate 114. The swivel flange plate is a circular disc with a concentric central opening 171 whose diameter approximates the nominal diameter of the spindle center pipe 112. The bottom end of the spindle center pipe is provided with a recess 169 on its outside surface forming a section of pipe of reduced diameter matching the inside diameter of the center opening 171 in the swivel flange plate and extending longitudinally the distance of approximately one half of the swivel flange plate thickness. The swivel flange plate is also provided with a bored hole 167 adjacent the center opening 171, whose diameter matches the diameter of the bored hole 159 in the hydraulic collar. The swivel flange plate is fitted over the bottom end of the spindle center pipe and the auxiliary hole 167 in the flange plate is aligned with the auxiliary hole 159 in the hydraulic coupling collar 160. The flange plate is firmly attached to the end of the spindle center pipe and a section of auxiliary pipe whose inside diameter matches the diameter of the bored holes in the flange plate and hydraulic coupling collar is aligned with the two bored holes 167 and 159 and attached to the top surface of the swivel flange plate 114 and extends to the bottom surface of the hydraulic coupling collar 160 and is attached thereto. Thus a continuous conduit for the passage of the air from the air chamber 152 in the swivel body upper housing 140 through the spindle collar 134, the hydraulic coupling collar 160, the auxiliary pipe 165 and through the swivel flange 1 14 is provided.

Finally, the swivel flange plate 114 is provided with a series of equally spaced bolt holes near its outer circumference which match with a series of equally spaced boltholes in the adapter top flange plate. The coupling of the kelly bar adapter top flange plate to the swivel flange plate is accomplished by fastening the two sections together with bolts 163. Hydraulic lines 234 are then attached to pass from the hydraulic outlet provided in the hydraulic coupling collar to the hydraulic attachments provided in the top surface of the adapter bottom flange plate 183. In this manner the hydraulic lines are coupled to the hydraulic cylinders 210 disposed within the Kelly Bar casing 220.

The spindle center pipe 112 is seen to extend up through the swivel body upper housing 140. Attached to the swivel body upper housing is an elbow 106. This elbow consists of a retainer plate 149 with a central opening 161 concentric with the central opening in the 

1. A combination drilling and belling tool for drilling an underground hole and then belling out a portion of the hole into a conical configuration on a single pass comprising: a generally cylindrical frame, the lower end of said frame forming a drilling bucket bottom; said frame having at least two exterior recesses formed in circumferentially spaced positions thereon and extending a substantial distance lengthwise of said frame; at least two elongated belling blades, said belling blades being normally received in respective ones of said recesses; means provided at the upper end of each of said recesses for pivotally supporting the upper end of the associated belling blade, whereby the lower end of each belling blade is movable in an arcuate path away from said frame; operating means coupled between said frame and said belling blades for selectively extending said blades in unison; and an elongated member disposed within and longitudinally movable relative to said frame, and coupled to said operating means for extending said blades when said elongated member is pulled upward; the intended mode of operation being such that said frame is first driven down and rotated with said blades in their normal position for drilling the hole by means of the drilling bucket bottom, then the downward movement of said drame is stopped and said elongated member is pulled upward while Said frame is rotated in order to accomplish the belling operation by means of said belling blades; wherein said frame includes a generally tubular outer shell in which said recesses are formed, a tubular drill stem concentrically disposed within and spaced away from said outer shell, and means at the upper end of said frame supporting said drill stem and said outer shell in fixed relationship to each other; and wherein said operating means includes a carriage disposed between said drill stem and said outer shell and normally positioned near the lower end of said frame, and a plurality of arms having their inner ends pivotally coupled to said carriage and their outer ends pivotally coupled to respective ones of said belling blades; said carriage being selectively movable upward relative to said frame and said elongated member being connected to said carriage for selectively raising the same.
 2. A combination drilling and belling tool as claimed in claim 1 which further includes first and second auxiliary pipes, of smaller diameter than said drill stem, and attached to the exterior surface of said drill stem in diametrically opposed portions thereon, said drill stem and auxiliary pipes extending to the upper end of said frame, one of said auxiliary pipes housing said elongated member and extending only a short distance down the length of said frame, the other of said auxiliary pipes being adapted for supply of a pressurized fluid to the hole and extending below the carriage when the carriage is in its lowermost position.
 3. The combination drilling and belling tool claimed in claim 1 wherein said carriage encircles said drill stem, and which further includes two pairs of rollers attached to the upper and lower ends of said carriage, respectively, and which rollingly support said carriage upon said drill stem; the inner ends of said operating arms being laterally displaced from the longitudinal axis of said carriage whereby the raising of said carriage tends to produce a counter-torque for rotating said carriage; and which further includes means providing a sliding lock between the outer surface of said carriage and the inner wall of said shell, whereby said carriage may slide up and down within said shell but its rotation is prevented.
 4. A combination drilling and belling tool as claimed in claim 1 wherein said carriage encircles said drill stem, and which further includes roller means supporting said carriage upon said drill stem, said drill stem acting both as a track for said carriage and as a conduit for removal of drilling chips from the hole.
 5. A combination drilling and belling tool as claimed in claim 4 wherein said drill stem extends to the lower end of said frame.
 6. A combination drilling and belling tool for drilling an underground hole and then belling out a portion of the hole into a conical configuration on a single pass comprising: a generally cylindrical frame, the lower end of said frame forming a drilling bucket bottom; said frame having at least two exterior recesses formed in circumferentially spaced positions thereon and extending a substantial distance lengthwise of said frame; at least two elongated belling blades, said belling blades being normally received in respective ones of said recesses; means provided at the upper end of each of said recesses for pivotally supporting the upper end of the associated belling blade, whereby the lower end of each belling blade is movable in an arcuate path away from said frame; operating means coupled between said frame and said belling blades for selectively extending said blades in unison; and an elongatd member disposed within and longitudinally movable relative to said frame, and coupled to said operating means for extending said blades when said elongated member is pulled upward; the intended mode of operation being such that said frame is first driven down and rotated with said blades in their normal position for drilling the hole by means of the drilling bucket bottom, then the downward movement of said frame is stopped and said elongated member is pulled upward while said frame is rotated in order to accomplish the belling operation by means of said belling blades; wherein said drilling bucket bottom is provided with blades having cutting edges adapted to cut in one predetermined direction of rotation of said frame, and said belling blades are provided with longitudinal cutting edges which are adapted to cut in the opposite direction of rotation of said frame.
 7. A combination drilling and belling tool as claimed in claim 6 wherein the cutting edge of each of said belling blades has a generally wedge shaped cross-section, thereby directing drilling chips towards the center of the drill hole.
 8. A combination drilling and belling tool for drilling an underground hole and then belling out a portion of the hole into a conical configuration on a single pass comprising: a generally cylindrical frame, the lower end of said frame forming a drilling bucket bottom; said frame having at least two exterior recesses formed in circumferentially spaced positions thereon and extending a substantial distance lengthwise of said frame; at least two elongated belling blades, said belling blades being normally received in respective ones of said recesses; means provided at the upper end of each of said recesses for pivotally supporting the upper end of the associated belling blade, whereby the lower end of each belling blade is movable in an arcuate path away from said frame; operating means coupled between said frame and said belling blades for selectively extending said blades in unison; and an elongated member disposed within and longitudinally movable relative to said frame, and coupled to said operating means for extending said blades when said elongated member is pulled upward; the intended mode of operation being such that said frame is first driven down and rotated with said blades in their normal position for drilling the hole by means of the drilling bucket bottom, then the downward movement of said frame is stopped and said elongated member is pulled upward while said frame is rotated in order to accomplish the belling operation by means of said belling blades; wherein aid operating means includes a carriage disposed within said frame and adapted for vertical reciprocation therein, and a plurality of arms having their inner ends pivotally coupled to said carriage and their outer ends pivotally coupled to respective ones of said belling baldes, said elogated member being coupled to said carriage for selectively raising the same; and wherein the inner end of each of said operating arms extends beside and beyond the longitudinal axis of said carriage, and is pivotally coupled to said carriage on the side therefrom opposite the respectively associated belling blade.
 9. A combination drilling and belling tool for drilling an underground hole and then billing out a portion of the hole into a conical configuration on a single pass comprising: a generally cylindrical frame having a lower end forming a drilling bucket bottom, and having at least two exterior recesses formed therein; at least two elongated belling blades normally received in respective ones of said recesses; means pivotally attaching the upper end of each of said belling blades to said frame whereby the lower end of each belling blade is movable in an arcuate path away from said frame; a tubular drill stem concentrically supported within said frame and extending to the lower end thereof, thus providing a channel for continuous fluid circulation so as to remove chips from the hole during both drilling and belling operations; and operating means for selectively extending said blades in unison, including a carriage disposed about said drill stem and a plurality of arms having their inner ends pivotally coupled to said carriage and their outer ends pivotally coupled to respective Ones of said belling blades; said operating means further including an elongated member coupled to said carriage and extending above said carriage beside said drill stem for selectively raising said carriage. 